Funds are requested to study how selective attention affects the responses of neurons in primary (SI) and secondary (SII) somatosensory cortex. Animals are trained to switch their focus of attention back and forth between different sensory systems, between different skin sites, between submodalities at a single skin site and between different sensory capacities subserved by a single submodality. The aim is to investigate the effects of attention on information processing in the somatosensory system. One possibility is that attention is not involved in the processing of information and simply "spotlights" a particular somatotopic location. Another, is that attention is an integral part of perception and selectively filters the responses of neurons critical for perception. Five specific aims are identified. The first is to investigate the differences in the pattern of neuronal firing when an animal's attention is diverted from touch to vision or audition while performing either a spatial or temporal discrimination task. The integration of information between touch and vision (or audition) may result in different neural effects during cross-modality tasks. The second aim is to investigate spatial tuning of attention by having the animal switch its attention between different locations on the same hand and between different locations on separate hands. The question addressed here is how tightly can attention be spatially focused. The third aim is to investigate whether different submodalities can be selectively engaged when attention is focused at a common skin site. Annals are presented with a vibrating spatial pattern on their finger tips and are required to discriminate either the spatial form or the pattern of vibration. The responses of SM (spatial form), RA (flutter) and PC (vibration) neurons that have receptive fields at a common skin site will be analyzed for modality specific affects. The fourth aim is to investigate whether different stimulus attributes (texture and form) subserved by the same submodality (SM) can be selectively engaged when attention is focused at a common skin site. The fifth aim is to investigate whether the neural responses cluster into modality specific columns or laminae. The data for this aim will come from experiments that address the first four aims. The point of examining the anatomical organization is that modality specific mechanisms may be restricted to operate within columns that are specific to a single stimulus attribute and that selective attention may function by either activating the responses within an entire column or by activating the responses within specific lamina within a column.